.box_1 {
  width: 100px;
  height: 100px;
  border-radius: 20px;
  background-color: aqua;
  display: flex;
  justify-content: center;
  align-items: center;
  color: black;
  animation: color 5s infinite;
}
@keyframes color {
  50%{
    color: coral;
  }
}